Question: Solve for $x$ and $y$ using substitution. ${5x-5y = 0}$ ${x = -4y+5}$
Explanation: Since $x$ has already been solved for, substitute $-4y+5$ for $x$ in the first equation. ${5}{(-4y+5)}{- 5y = 0}$ Simplify and solve for $y$ $-20y+25 - 5y = 0$ $-25y+25 = 0$ $-25y+25{-25} = 0{-25}$ $-25y = -25$ $\dfrac{-25y}{{-25}} = \dfrac{-25}{{-25}}$ ${y = 1}$ Now that you know ${y = 1}$ , plug it back into $\thinspace {x = -4y+5}\thinspace$ to find $x$ ${x = -4}{(1)}{ + 5}$ $x = -4 + 5$ ${x = 1}$ You can also plug ${y = 1}$ into $\thinspace {5x-5y = 0}\thinspace$ and get the same answer for $x$ : ${5x - 5}{(1)}{= 0}$ ${x = 1}$